#include <iostream>
#include <vector>
#include <string>
#include <queue>
#include <unordered_map>
// 交错字符串：https://leetcode.cn/problems/interleaving-string/description/
using namespace std;
class Solution {
public:
    bool isInterleave(string s1, string s2, string s3) {
        int m=s1.size();
        int n=s2.size();
        if((m+n)!=s3.size()) return false;
        s1=" "+s1;
        s2=" "+s2;
        s3=" "+s3;
        vector<vector<bool>> dp(m+1,vector<bool>(n+1));
        dp[0][0]=true;
        for(int i=1;i<=m;i++)
        {
            if(s1[i]==s3[i])
                dp[i][0]=true;
            else 
                break;
        }
        for(int j=1;j<=n;j++)
        {
            if(s2[j]==s3[j])
                dp[0][j]=true;
            else
                break;
        }
        for(int i=1;i<=m;i++)
        {
            for(int j=1;j<=n;j++)
            {
                //dp[i][j]=(s1[i]==s3[i+j]&&dp[i-1][j])||(s2[j]==s3[i+j]&&dp[i][j-1]);
                if(s1[i]==s3[i+j]&&s2[j]==s3[i+j])
                    dp[i][j]=dp[i-1][j]||dp[i][j-1];
                else if(s1[i]==s3[i+j])
                    dp[i][j]=dp[i-1][j];
                else if(s2[j]==s3[i+j])
                    dp[i][j]=dp[i][j-1];
                
            }
        }
        return dp[m][n];
    }
};